The focus of this Center is the sperm cell as a contraceptive target. Remarkable advances have occurred recently in cell and molecular biology, immunology and fertilization research. These advances have combined to open new possibilities for contraceptive intervention, directed against sperm cells, that may have been previously imagined but were unattainable. Anti-sperm contraception can target sperm function or sperm development. Our Center's projects include both targets. The major theme of our Center is immunocontraception to block sperm function. Our Center is actively studying sperm plasma membrane proteins that function in sperm-egg interaction. Immunization of males or females with these proteins can induce infertility because sperm function in gamete interaction is blocked by attached antibodies. A second theme is to block sperm development. Novel immunological and pharmacological strategies to derail the complex process of sperm production are proposed here. In the previous grant period, our Center devote all its efforts to the first theme, immunocontraception to block sperm function. However, all of us who study sperm function are aware of advances in spermatogenesis research and realized that new, feasible contraceptive targets sperm development are being identified. Thus, we have proposed an expansion of our target list to include sperm development, increasing our scope and chances of developing contraceptive products.